Figure 6.

Esterification degree of the different lignin fractions with various fatty acids. The reactions were performed using 1 molar equivalent of fatty acid with respect to the aliphatic OH groups in lignin, using acetone as a solvent, and catalyzed by lipase at 20 °C for 72 h. The amount of remaining free aliphatic OH groups after esterification was quantified by ³¹P-NMR in every reaction as mmol/g sample (including the residual fatty acid) and it was converted to mmol/g of lignin by multiplying the value with the mass % of lignin in the sample. The corrected value was then compared to the aliphatic OH content (mmol/g lignin) in the original lignin fractions in order to calculate the esterification degree.